This invention relates to a process for polymerizing olefins. In another aspect, this invention relates to a process for making a polymerization catalyst. In another aspect, this invention relates to a process for polymerizing alpha-olefins using a catalyst system wherein the catalyst is prepared by a novel process. In another aspect, this invention relates to a novel process for forming a catalyst which can be used with a cocatalyst to form a catalyst system for the polymerization of alpha-olefins. In yet another aspect, the invention relates to a composition of matter useful as a catalyst precursor.
It is known to polymerize alpha-olefins and mixtures thereof at low pressures with coordination catalysts. In these processes, the catalysts used are prepared from mixtures of compounds of transition elements of Subgroups IVB, VB, VIB of the Periodic Table and the hydrides or organometallic compounds of the elements of Groups I to III of the Periodic Table. The Periodic Table referred to herein is as shown on page B-2, 45th Edition (1964), of the Handbook of Chemistry and Physics, Chemical Rubber Co. The polymerization is generally carried out in suspension, in solution or even in a gaseous phase.
Because of greater process economics, it is desirable to carry out olefin polymerization reactions, particularly polymerization reactions involving ethylene and predominantly ethylene-containing copolymers in an inert diluent at a temperature at which the resulting polymer does not go into solution, with the polymer being recovered without elaborate steps to remove the catalyst. In order for this more economical method of manufacture to be feasible from a practical standpoint the catalyst must be capable of producing polymer in high productivities in order to maintain the residual catalyst level in the final polymer at a very low level. The activity of an olefin polymerization catalyst is thus one important factor in the continuous search for a catalyst useful for the polymerization of alpha-olefins. It is also desirable that the process used in forming the catalyst be such as to allow ease in preparation and to allow control over the final catalyst formed. It is further desirable to provide a catalyst for producing polyolefins suitable for use in rotational molding processes.
In addition to catalyst productivity another important aspect of a polymerization process and catalyst is the properties of the polymer particles produced. It is desirable to produce polymer particles which are characterized by strength, uniformity of size, and relatively low amount of fines. Although polymer fluff having relatively high percentages of fines can be handled with plant modifications, production of a polymer in high productivity with low fines content is highly desirable.